THIS AVALANCHE ADVISORY EXPIRED ON February 9, 2017 @ 6:46 am
Avalanche Advisory published on February 8, 2017 @ 6:46 am
Issued by Brandon Schwartz - Tahoe National Forest

MODERATE avalanche danger exists for all elevations today. Wet loose and wind slab avalanche problems remain an ongoing concern. Precipitation intensity will be dramatically less today than yesterday and the snowpack has had time to establish drainage for rain on snow. Human triggered avalanches remain possible today. Natural avalanches are unlikely, but not impossible today in isolated areas. Exercise caution for travel in or below backcountry avalanche terrain.

 

2. Moderate

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Above Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Near Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.

2. Moderate

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Below Treeline
Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
    Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1: Loose Wet
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Rain soaked surface snow below 8,500' to 9,000' will remain prone to wet loose avalanche problems today. The vast majority of wet loose avalanche activity is expected to be human triggered and occur on any aspect where wet surface snow exists. This avalanche problem will exist on slopes steeper than 35 degrees.

Consider how terrain features below such as cliffs or terrain traps could magnify the consequences of being pushed around by a wet loose avalanche.

Avalanche Problem 2: Wind Slab
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Above 8,500' to 9,000' where significant amounts of new snow have accumulated, wind slab avalanche problems remain an ongoing concern. Unstable wind slabs are most likely to exist near treeline and above treeline on NW-N-NE-E-SE-S aspects on slopes 35 degrees and steeper. Wind slabs could exist in isolated areas below treeline or on SW-W aspects as well due to the strength of the recent winds. Avalanche size could be fairly large at the upper elevations.

Looks for signs of recent wind loading such as cornice features and wind pillows to help identify where problematic wind slabs are likely to exist.

recent observations

Observations made yesterday on Andesite Ridge (Donner Summit area) revealed that a widespread cycle of wet slab avalanches had occurred from rain on recent new snow. Some avalanches appeared older than others indicating that the cycle was not limited to a short specific time window. Signs of numerous avalanches size D1 and D2 were seen on N-NE-E-SE aspects in the Donner Summit area. Significant amounts of standing and running water were noted at pass level (7,227'). Poor visibility greatly limited the ability to see signs of avalanche activity in the higher surrounding terrain.

Weather and CURRENT CONDITIONS
weather summary

A brief break in precipitation intensity will occur today. Lingering moisture will keep rain and snow showers ongoing with snow level 8,500' to 9,000'. Ridgetop winds remain out of the SW and are forecast at strong to gale force in speed. Ridgetop gusts to 90 mph are expected today. The next storm system moves into the region tomorrow. Winds will increase overnight and tomorrow morning with ridgetop gusts returning to the 95 to 145 mph range. Snow levels are expected to remain at 8,000' to 9,000' through most of this next storm. Snow level is expected to fall below 6,000' Friday night at the tail end of the precipitation event.

Weather observations from along the Sierra Crest between 8200 ft. and 8800 ft.
0600 temperature: 34 to 35 deg. F.
Max. temperature in the last 24 hours: 35 to 39 deg. F.
Average wind direction during the last 24 hours: SW
Average wind speed during the last 24 hours: 60 mph
Maximum wind gust in the last 24 hours: 148 mph
New snowfall in the last 24 hours: Rain 3 to 5 in, Snow 0 to 2 inches
Total snow depth: 115 to 152 inches
Two-Day Mountain Weather Forecast Produced in partnership with the Reno NWS
For 7000 ft. to 8000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloudy skies, becoming cloudy. Rain showers. Cloudy skies with a chance of rain showers. Cloudy skies with a slight chance of rain in the morning. Rain and snow in the afternoon. Snow level 8,500' lowering to 7,500'.
Temperatures: 39 to 43 deg. F. 33 to 38 deg. F. 39 to 44 deg. F.
Wind Direction: SW SW SW
Wind Speed: 15 to 25 mph with gusts to 45 mph. Gusts increasing to 55 mph in the afternoon. 20 to 30 mph. Gusts to 65 mph increasing to 85 mph after midnight. 25 to 35 mph increasing to 30 to 50 mph in the afternoon. Gusts to 95 mph.
Expected snowfall: 0 in. 0 in. Up to 4 in.
For 8000 ft. to 9000 ft.
Wednesday Wednesday Night Thursday
Weather: Mostly cloud skies, becoming cloudy. Showers in the morning. A chance of showers in the afternoon. Snow level 8,500' to 9,000'. Mostly cloudy skies. Showers likely in the evening. A chance of showers after midnight. Cloudy skies. A slight chance of rain and snow in the morning. Rain and snow in the afternoon.
Temperatures: 32 to 38 deg. F. 30 to 35 deg. F. 32 to 37 deg. F.
Wind Direction: SW SW SW
Wind Speed: 25 to 35 mph with gusts to 80 mph, increasing to 30 to 45 mph with gusts to 90 mph in the afternoon. 35 to 50 mph with gusts to 110 mph, increasing to 45 to 60 mph with gusts to 130 mph after midnight. 60 to 80 mph. Gusts to 145 mph decreasing to 130 mph in the afternoon.
Expected snowfall: 2 to 4 in. 0 to 1 in. 4 to 6 in.
Disclaimer

This avalanche advisory is provided through a partnership between the Tahoe National Forest and the Sierra Avalanche Center. This advisory covers the Central Sierra Nevada Mountains between Yuba Pass on the north and Ebbetts Pass on the south. Click here for a map of the forecast area. This advisory applies only to backcountry areas outside established ski area boundaries. This advisory describes general avalanche conditions and local variations always occur. This advisory expires 24 hours after the posted time unless otherwise noted. The information in this advisory is provided by the USDA Forest Service who is solely responsible for its content.

For a recorded version of the Avalanche Advisory call (530) 587-3558 x258